THE PROCESS

Continuous galvanised steel or Aluminium Zinc coated steel is manufactured under precise, factory controlled conditions in which flat rolled steel coils are upgraded to high quality coated steel using high speed continuous lines that control not only the coating quality but also the strength and malleability of the steel product.
Essentially the flat steel strip is dipped through a kettle of either molten Zinc or molten Aluminium-Zinc alloy and recoiled to give the finished coated products.

THE COATING LINE

The new coating line at MRM uses state-of-the-art technology that is the only one of its kind in the entire African Continent. It has a dual facility for coating both Zinc and 55% Aluminium-Zinc alloy with a capacity of 80,000 tonnes per annum.

ENVIRONMENT FRIENDLY TECHNOLOGY

Coils of rolled steel are continuously unwound and fed through cleaning and annealing sections. The NOF technology uses thermal cleaning with LPG flame and a mixture of Nitrogen and Hydrogen gases for preparing the steel surface. This leaves no residues on the strip and ensures excellent adherence of the coating to the strip surface. It also greatly minimizes the emmisions from the line providing a friendly environment to operate under.

The treated steel surface is then fed into either one of the two molten baths at speeds of up to 150 meters per minute. As the steel exits the molten baths, gas ‘knives’ wipe off the excess coating from the steel sheet to control the coating thickness.

An on-line X-ray coating weight gauge ensures accuracy and uniformity of coating across the length and width of the sheet. This increases the life of the sheet as low coating spots are avoided.

The steel strip then undergoes a series of mechanical or chemical requirements depending on the end use application. All coatings are metallurgically bonded to the steel they protect. This ensures coating adhesion, which is critical for the consequent manufacturing process that gives the steel its final product shape.

The NOF type of line also gives a unique pattern (only available from such lines) on a galvanised surface, called spangle, which has a special aesthetic appeal.